316L stainless steel pipe
316L is a stainless steel material grade, AISI 316L is the corresponding American grade, and sus 316L is the corresponding Japanese grade. China's unified digital code is S31603, the standard grade is 022Cr17Ni12Mo2 (new standard), and the old grade is 00Cr17Ni14Mo2, which means it mainly contains Cr, Ni, and Mo, and the numbers indicate the approximate percentage. The national standard is GB/T 20878-2007 (current version).
316L is widely used in the chemical industry because of its excellent corrosion resistance. 316L is also a derivative of 18-8 austenitic stainless steel, with 2 to 3% Mo added. On the basis of 316L, many steel types are derived. For example, 316Ti is derived by adding a small amount of Ti, 316N is derived by adding a small amount of N, and 317L is derived by increasing the Ni and Mo content.
Most of the 316L currently on the market is produced in accordance with American standards. For cost considerations, steel mills generally limit the Ni content of products as low as possible. The American standard stipulates that the Ni content of 316L is 10 to 14%, and the Japanese standard stipulates that the Ni content of 316L is 12 to 15%. According to the minimum standard, there is a 2% difference in Ni content between the American standard and the Japanese standard, which is still quite huge in terms of price. Therefore, customers still need to see clearly when purchasing 316L products whether the product refers to ASTM or JIS standards.
The Mo content of 316L makes this steel type have excellent corrosion resistance and can be safely used in environments containing halogen ions such as Cl-. Since 316L is mainly used for its chemical properties, steel mills have slightly lower surface inspection requirements for 316L (compared to 304). Customers with higher surface requirements should strengthen surface inspection.
Corrosion resistance
Excellent performance in a variety of atmospheric environments and many corrosive media - often more corrosion resistant than 304. Pitting and crevice corrosion can occur in warm chloride environments, and stress corrosion cracking can occur at temperatures above about 60 °C. Tolerates drinking water with chloride contents up to approximately 1000 mg/L at ambient temperature, reducing to approximately 500 mg/L at 60 °C.
316 is often considered the standard "marine grade stainless steel", but it is not resistant to warm seawater. In many marine environments, 316 does exhibit surface corrosion, often manifesting as brown staining. This is especially relevant for cracks and rough surface finishes.
heat resistance
Good oxidation resistance in intermittent operation at 870 °C and continuous operation at 925 °C. If subsequent resistance to water corrosion is important, continuous use of 316 in the range 425-860 °C is not recommended. The 316L grade is more resistant to carbide precipitation and can be used within the above temperature range. Grade 316H has greater strength at elevated temperatures and is sometimes used in structural and pressure-bearing applications at temperatures above about 500 °C.
heat treatment
Solution treatment (annealing) - heating to 1010-1120 °C and rapid cooling. These grades cannot be hardened by heat treatment.
welding
Excellent weldability with all standard fusion and resistance methods, with or without filler metal. Heavy-duty welded parts in Grade 316 require post-weld annealing for maximum corrosion resistance. This is not required for the 316L.
316L stainless steel generally cannot be welded using oxyacetylene welding methods.
processing
316L stainless steel tends to work harden if machined too quickly. Therefore, low speed and constant feed rate are recommended.
316L stainless steel is also easier to machine than 316 stainless steel due to its lower carbon content.
Hot working and cold working
316L stainless steel can be thermally processed using the most common thermal processing techniques. The optimal thermal processing temperature should be in the range of 1150-1260℃, and of course should not be lower than 930℃. Post-process annealing should be performed to produce maximum corrosion resistance.
The most common cold working operations, such as shearing, drawing, and stamping, can be performed on 316L stainless steel. Annealing should be performed after processing to eliminate internal stress.
Hardening and work hardening
316L stainless steel does not harden due to heat treatment. It can be hardened by cold working, which also increases strength.
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